2005 YAMAHA YFM660R engine

8-47 1. Spark plug cap
1. Capuchon de bougie
1. Tapa de bujía
1. Spark plug wrench
1. Clé à bougie
1. Llave de bujía
EBU14550
Spark plug inspection
Removal
1. Remove the spark plug cap.
2. Use the spark plug wrench in the owner’s tool
kit to remove the spark plug as shown.
Inspection
The spark plug is an important engine component
and is easy to inspect. The condition of the spark
plug can indicate the condition of the engine.
The ideal color on the white insulator around the
center electrode is a medium-to-light tan color for
an ATV that is being ridden normally.
Do not attempt to diagnose such problems your-
self.
Instead, take the ATV to a Yamaha dealer. You
should periodically remove and inspect the spark
plug because heat and deposits will cause the
spark plug to slowly break down and erode. If elec-
trode erosion becomes excessive, or if carbon and
other deposits are excessive, you should replace
the spark plug with the specified plug.
U5LP64.book Page 47 Thursday, April 1, 2004 4:53 PM

8-53 1. Check hose
1. Flexible de contrôle
1. Manguito de comprobación
1. Air filter case cover 2. Holder (× 6)
1. Couvercle du boîtier de filtre à air 2. Support (× 6)
1. Tapa de la caja del filtro 2. Soporte (× 6)
EBU12121
Air filter element cleaningNOTE:_ There is a check hose at the bottom of the air filter
case. If dust or water collects in this hose, empty
the hose and clean the air filter element and air fil-
ter case. _1. Remove the seat. (See page 4-33 for seat re-
moval and installation procedures.)
2. Remove the air filter case cover by unhook-
ing the holders.
3. Remove the air filter element.
4. Remove the air filter element from its frame.
5. Wash the air filter element gently but thor-
oughly in solvent.
WARNING
_ Always use parts cleaning solvent to clean the
air filter element. Never use low flash point sol-
vents or gasoline to clean the air filter element
because the engine could catch fire or ex-
plode. _
U5LP64.book Page 53 Thursday, April 1, 2004 4:53 PM

8-57 1. Hose
1. Flexible
1. Manguera
11. Install the air filter case cover and be sure to
connect the hose.
12. Install the seat.NOTE:_ The air filter element should be cleaned every 20–
40 hours. It should be cleaned and lubricated more
often if the machine is operated in extremely dusty
areas. Each time air filter element maintenance is
performed, check the air inlet to the air filter case
for obstructions. Check the air filter element rubber
joint to the carburetor and manifold fittings for an
airtight seal. Tighten all fittings securely to avoid
the possibility of unfiltered air entering the engine. _CAUTION:_ Never operate the engine with the air filter ele-
ment removed. This will allow unfiltered air to
enter, causing rapid engine wear and possible
engine damage. Additionally, operation with-
out the air filter element will affect carburetor
jetting with subsequent poor performance and
possible engine overheating. _
U5LP64.book Page 57 Thursday, April 1, 2004 4:53 PM

8-59
EBU15160
Carburetor adjustment
The carburetors are vital parts of the engine and
require very sophisticated adjustment. Most ad-
justing should be left to a Yamaha dealer who has
the professional knowledge and experience to do
so. However, the idling speed may be performed
by the owner as a part of the usual maintenance
routine.CAUTION:_ The carburetors were set at the Yamaha facto-
ry after many tests. If the settings are dis-
turbed by someone without sufficient
technical knowledge, poor engine perfor-
mance and damage may result. _
U5LP64.book Page 59 Thursday, April 1, 2004 4:53 PM

8-61 1. Throttle stop screw
1. Vis d’arrêt de l’accélérateur
1. Tornillo de tope del acelerador
EBU13020
Idle speed adjustmentNOTE:_ A diagnostic tachometer must be used for this pro-
cedure. _1. Start the engine and warm it up for a few min-
utes at approximately 1,000 to 2,000 r/min.
Occasionally rev the engine to 4,000 to
5,000 r/min. The engine is warm when it
quickly responds to the throttle.
2. Connect the tachometer to the spark plug
lead, and then set the idle to the specified
idling speed by adjusting the throttle stop
screw. Turn the screw in direction
a to in-
crease the engine speed, and in direction
b
to decrease the engine speed.
Specified idle speed:
1,450–1,550 r/min
U5LP64.book Page 61 Thursday, April 1, 2004 4:53 PM

8-63 1. Locknut 2. Adjusting bolt
a. Throttle lever free play
1. Contre-écrou 2. Boulon de réglage
a. Jeu du levier d’accélération
1. Contratuerca 2. Perno de ajuste
a. Juego libre de la palanca del acelerador
EBU00307
Throttle lever adjustmentNOTE:Adjust the engine idling speed before adjusting the
throttle lever free play.1. Loosen the locknut.
2. Turn the adjusting bolt until the throttle lever
free play is 3–5 mm.
3. Tighten the locknut.
U5LP64.book Page 63 Thursday, April 1, 2004 4:53 PM

8-65
EBU00303
Valve clearance adjustment
The correct valve clearance changes with use, re-
sulting in improper fuel/air supply or engine noise.
To prevent this, the valve clearance must be ad-
justed regularly. This adjustment however, should
be left to a professional Yamaha service techni-
cian.
U5LP64.book Page 65 Thursday, April 1, 2004 4:53 PM

8-93
2. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with a
special O-ring chain lubricant.CAUTION:
Do not use engine oil or any other lubricants
for the drive chain, as they may contain sub-
stances that could damage the O-rings.
U5LP64.book Page 93 Thursday, April 1, 2004 4:53 PM